| 摘要 |
<p>An underground storage reservoir for LNG or other fluids at cryogenic temperatures comprises an underground cavern 10, usually insulated, in which the cryogenic fluid is stored, an inner circulation system surrounding the cavern and comprising a plurality of passages in or adjacent the cavern wall or in the ground immediately surrounding the wall, and an outer circulation system comprising a plurality of ducts surrounding and spaced from the inner circulation system. During operation of the reservoir to store a cryogenic fluid, a heat exchange medium is circulated through the passages of the inner circulation system so that the temperature of the cavern wall and the ground immediately surrounding the wall is maintained within a predetermined temperature range higher than the temperature of the stored fluid, and so that water vapour which enters the passages from the surroundings is absorbed and removed by the heat exchange medium. In addition, a heat exchange medium is also circulated through the ducts of the outer circulation system so that water in the ground surrounding the ducts is frozen to form a frozen zone in the ground spaced from and encircling the cavern and the inner circulation system. This frozen zone halts the otherwise continuous drainage of water into the reservoir area from the surrounding ground both during construction of the cavern and the inner circulation system and during subsequent operation of the reservoir. In addition, the operation of the inner and outer circulation systems serve to substantially reduce the rate at which water vapour migrates through the ground in the reservoir area towards the storage cavern. The inner and outer circulation systems of the reservoir can also be used to perform other functions, such as the sealing of cracks in the ground within the reservoir region by distributing sealing substances under pressure, collecting and removing any stored product which may have leaked into the ground from the cavern, and perhaps also, by suitably adjusting the operating pressures, causing gas to diffuse outwards through the ground to the outer circulation system in counterflow to water vapour migrating inwards.</p> |
